This application relates generally to fireproofing products and more specifically to fireproofing panels.
Fireproofing is an important segment of an overall fire protection system to protect people and property. The fireproofing is applied over some type of substrate. Typically, fireproofing is applied to structural members in areas where a fire can occur. In the event of fire, fireproofing will retard the rate of temperature increase in the structural members such that the failure temperature of the members can be delayed for as much as several hours. During the period of delay, the fire may be extinguished or, at the least, the structure can be safely evaluated. When no fireproofing is used, structural members have been known to fail, thus resulting in structure collapse, in less than 15 minutes.
Fireproofing is also applied to elements such as walls, bulkheads, or decks. In a fire, the fireproofing delays an increase in temperature behind the element. Where inflammable material is stored behind the element, the fireproofing can prevent ignition of the material, hopefully until the fire is extinguished.
Fireproofing is also applied to pressure vessels. The fireproofing reduces the possibility that the vessel will rupture. Thus, the fireproofing reduces the chance of explosion or release of hazardous material from the vessel.
Fireproofing is also used over cable trays. The fireproofing can keep the circuitry in the tray functioning for an extended period of time in the event of a fire.
One widely used type of fireproofing is a char-forming coating. The coating can be called ablative, subliming, or intumescent. As supplied, these coatings can be in the form of a low viscosity paint or a high viscosity mastic. These coatings are sprayed or troweled or brushed on to a substrate.
Some of these coatings are used in combination with a mesh element. Some coatings utilize a flammable mesh, others a nonflammable mesh such as one fabricated from steel. With some coatings, the mesh is mechanically mounted on the substrate; with others, it is simply embedded in the coating.
When these coatings are exposed to a fire, they undergo a number of changes of state--solid to liquid, liquid to gas, and solid to gas--absorbing some of the energy of the fire, and insulating the substrate. Fire exposure results in the formation of a char which, depending on the material, can be thicker, as thick, or less thick than the thickness of the non-fire exposed coating.
The above-mentioned mesh element may perform one or more functions. Mesh might be used to retain char on the substrate during a fire. It also reduces the mismatch in coefficient of thermal expansion between the fireproof coating and the substrate, such as steel or concrete. It thus serves to keep the coating from peeling off the substrate, especially in environments where the temperature cycles through a large range. In other instances, the mesh reinforces the fireproofing prior to a fire to reduce damage to the coating of fireproofing which could be caused by impact or movement of the substrate.
One example of a fireproofing compound which forms a char is CHARTEK intumescent epoxy coating sold by Textron Specialty Materials of Lowell, Mass., USA. Other such materials are described in U.S. Pat. No. 3,849,178 issued to Feldman.
It has been suggested that the cost of installing fireproofing could be reduced if the substrate were covered with fireproofing panels. Panels could be installed without the special equipment needed to apply coatings of fireproofing material. Also, surface preparation needed before a coating can be applied could be eliminated if panels were used. Further, a coating can be applied to an outside structure only if weather conditions are favorable while the coating is applied and is curing. Installation of panels is much less dependent on weather conditions.
Panels made of fireproofing material similar to concrete are commercially available. For example, U.S. Pat. No. 4,567,705 to Carlson describes such panels. To protect a substrate, steel studs are welded to the substrate in a predetermined pattern. The stud positions match holes in the panels. The panels are then mounted on the studs and bolted to the substrate.
To cover a substrate larger than a single panel, many panels are mounted to the substrate. The panels are butted together. The space between the panels is caulked to provide a barrier to moisture. The panels are, however,very heavy and are difficult to install in some places. Also, such panels are not used where the fireproofing must have an A or a H rating.
Lightweight pieces made from char forming compounds have also been suggested. U.S. Pat. No. 4,493,945 shows lightweight pieces of fireproofing material used to cover a substrate. Relatively complicated fastening mechanisms are employed. Moreover, it is necessary to still use char-forming compound in its liquid (mastic) form to seal the seams between pieces.
The pieces shown in U.S. Pat. No. 4,493,945 have also been formed as panels. The panels are attached to walls or large substrates by bolting them to studs mounted to the substrate. The joints between panels and the bolts are then covered by char-forming compound in liquid form.
While there are many advantages to using panels, suitable methods to install fireproofing panels to some structures have not been developed. For example, some offshore platform decks used by the hydrocarbon industry rest on a small number of concrete joists or beams. These platform decks are used in oil or gas drilling or for hydrocarbon processing. To support the weight of the platform deck, each joist has a cross section over 25 feet square. The joists are traditionally cast in a ship building yard and then floated to the site where the oil drilling platform is to be installed.
To provide high strength but low weight, the joists are made with specially modified concrete. While concrete is generally resistant to fire and in some circumstances is even used as a fireproofing material, this specially modified concrete may be weakened in a fire. Also, because of the serious consequences if a beam or joist fails, it is desirable to place fireproofing over the concrete to help prevent the reinforcing metal inside the joist from reaching its failure temperature.
Because of the large size of these joists and because of the location of the joists below the oil drilling platform deck, it is difficult to apply fireproofing to these joists.